Non-tachyonic open descendants of the 0B string theory

We use the crosscap constraint to construct open descendants of the 0B string compactified on $T^6\mathrm{/}{Z}_3$ and on $T^4\mathrm{/}{Z}_2$ free of tachyons both in the closed and in the open unoriented sectors. In four dimensions the construction results in a Chan-Paton gauge group $U(8)\otimes U(12)\otimes U(12)$ with three generations of chiral fermions in the representations $(\bar{8},1,\overline{12})+(8,12,1)+(1,\overline{66},1)+(1,1,66)$.